Polypropylene and polyethylene have enjoyed wide commercial success because of their outstanding performance and cost characteristics. Because of their impact resistance and ability to withstand weather extremes, blends of polypropylene and ethylene-α-olefin copolymer elastomers and plastomers have found particular use in injection molded structures such as automobile bumpers and fascias, interior panels, and other parts.
Relatively large parts such as automobile bumpers present particular challenges in their fabrication and in the ability to impart the necessary stiffness and impact balance to the particular injection molded part. For example, the ability to tailor the desired stiffness/impact balance to a compound and its injection molded part may require the use of “compatibilizers” between the polypropylene and the ethylene-based copolymers used in the compound formulations. Other injection molding issues such as cold flow, tiger striping and gel formation must also be addressed, which also may require various additives. For example, small dots or “gels” may appear at the surface of the final shaped article due to poor dispersion of the polymeric components. However, polyolefin compositions that have been developed to reduce cold flow, tiger striping and gel problems are often not suitable as compatibilizers for delivering improved or enhanced stiffness and impact balance.
Therefore, there is a continuing need for new or improved polyolefin compositions that can be blended or combined with various other polyolefin materials, to provide final compounds exhibiting a good balance of physical and surface properties. It would be advantageous if the new polyolefin compositions could be used as a compatibilizer that could be added to a wide variety of polyolefin compounds that are ready for an injection molding process. This unfulfilled need includes the need for associated methods that relate to the preparation and use of any new compositions that can impart a balance of good physical and surface properties to the final compound.